The present invention relates to a collision or reaction device for a mass spectrometer, a mass spectrometer, a method of colliding or reacting ions and a method of mass spectrometry. The preferred embodiments relates to a gas phase reaction device that facilitates the removal of the gas phase reaction ionic products in a controlled manner. The gas phase reaction device may comprise an ion-ion, ion-electron, ion-molecule or ion-metastable reaction device.
GB-2467466 (Micromass) discloses a high transmission RF ion guide with no physical axial obstructions wherein an applied electrical field may be switched between two modes of operation. In a first mode of operation the device onwardly transmits a mass range of ions and in a second mode of operation the device acts as a linear ion trap in which ions may be mass selectively displaced in at least one radial direction and subsequently ejected adiabatically in the axial direction past one or more radially dependent axial DC barriers.
It is known that mass selective radial displacement may be achieved by arranging the frequency of a supplementary time varying field to be close to a mass dependent characteristic frequency of oscillation of a group of ions within the ion guide.
The characteristic frequency is the secular frequency of ions within the ion guide. The secular frequency of an ion within the device is a function of the mass to charge ratio of the ion and is approximated by the following equation (reference is made to P. H. Dawson, Quadrupole Mass Spectrometry and Its Applications) for an RF only quadrupole:
                              ω          ⁡                      (                          m              z                        )                          ≈                                            2                        ·            z            ·            e            ·            V                                m            ·                          R              0              2                        ·            Ω                                              (        1        )            wherein m/z is the mass to charge ratio of the ion, e is the electronic charge, V is the peak RF voltage, R0 is the inscribed radius of the rod set and ω is the angular frequency of the RF voltage.
It is known to provide a broadband excitation to a quadrupole ion guide with frequency components missing around the secular frequency of an ion. The frequency components which are missing are commonly referred to as notches. Multiple ions may be isolated in the ion guide by applying additional notches or missing frequencies.
U.S. Pat. No. 7,355,169 (McLuckey) discloses a method of peak parking. This method is based around allowing all reactant products to remain in an ion trap and only ejecting a known product ion and is specific to ion-ion reactions.
U.S. Pat. No. 5,256,875 (Hoekman) discloses a method of generating an optimised broadband filtered noise signal which may be applied to an ion trap. The broadband signal is filtered by a notch filter to generate a broadband signal whose frequency-amplitude has one or more notches. An arrangement is disclosed which enables rapid generation of different filtered noise signals.
FIG. 2 of WO 2012/051391 (Xia) relates to an arrangement wherein a broadband notched signal is applied to a linear ion trap having multiple frequency notches so as to isolate parent ions m1. The parent ions m1 are then fragmented by applying a discrete frequency component to form resultant fragment ions m2. The resulting fragment ions m2 are retained within the ion trap by virtue of the broadband notched signal having a frequency notch corresponding to m2.
FIG. 11(b) of WO 00/33350 (Douglas) relates to an arrangement wherein a broadband notched waveform is applied in order to isolate triply charged parent ions having a mass to charge ratio of 587. The parent ions are fragmented to produce fragment ions as shown in FIG. 11(c). The dominant fragment ions having a mass to charge ratio of 726 are then isolated as shown in FIG. 11(d). First generation fragment ions having a mass to charge of 726 are then fragmented to form second generation fragment ions as shown in FIG. 11(e).
GB-2455692 (Makarov) discloses a method of operating a multi-reflection ion trap.
US 2009/0090860 (Furuhashi) discloses an ion trap mass spectrometer for MSn analysis.
GB-2421842 (Micromass) discloses a mass spectrometer with resonant ejection of unwanted ions.
GB-2452350 (Micromass) discloses a mass filter using a sequence of notched broadband frequency signals.
US 2010/0276583 (Senko) discloses a multi-resolution mass spectrometer system and intra-scanning method.
It is desired to provide an improved collision or reaction device for a mass spectrometer and an improved method of colliding or reacting ions.